Whenever I reboot my OMV system, normally after updates, it is not accessible over the LAN on it's DHCP IP address, and within OMV, DNS resolution fails.
This started in the last couple of weeks from memory, but I'm not confident about correlating it to any specific config changes.
Upon reboot, the address 192.168.0.15 which it gets by DHCP through MAC allocation on my PiHole does not respond.
Fortunately, a KVM running on OMV with autostart, which has a bridged macvtap is accessible, on 192.168.0.17
Connecting to that VM and using it to load OMV on 192.168.122.1 lets me access the Workbench no problem, same for SSH. External DNS entries do not resolve at this point.
Editing the network interface in Workbench in a negligible way via this route, e.g. swapping from DHCP to a static IP address, or just setting a static DNS server rather than a DHCP'd one, then pressing save and applying the changes then makes the server accessible as normal, until the next reboot.
Prior to a couple of weeks ago, I could reboot without any problem.
I have looked at netplan, as per someone else having a reboot related problem, but didn't see the same sort of stuff as them, and I've done simple stuff like ip link card down&& ip link card up which don't work, but the VM based network change works. I have looked into dmesg with nothing obvious showing.
I did have to install the Zabbly kernel when I first installed OMV as my onboard NIC was not supported, but that has been in place since I built this installation several months ago.
Whilst I do have a workaround, I'd really like to get to the root cause of this and can provide any log files etc required that may help diagnose this and get me back to being able to reboot without worrying about it!
